Synthesis and properties of highly branched polycations with an aliphatic polyether scaffold

Synthesis and Properties of Highly Branched Polycations with an Aliphatic Polyether Scaffold

ERNST SCHWAB, STEFAN MECKING

Fachbereich Chemie, Universitat Konstanz, Universitatsstrar.!,e 10, 78457 Konstanz, Germany

Received 22 March 2005; accepted 15 June 2005 DOl: 10.1002/pola.20983

Published online 23 August 2005 in Wiley lnterScience (www.interscience.wiley.com).

ABSTRACT: Cationic polyelectrolytes with pyridinium and 1,2-dimethylimidazolium functionalities based on a hyperbranched polyglycerol scaffold with a narrow polydis- persity were prepared by a polymer analogous reaction in a one-pot synthesis. By the variation of the spacer lengths between the cationic functionalities and polyether scaffold, a simple method was developed to adjust the charge density and flexibility of the polycations, as reflected by their glass-transition temperature. The polyelectro- lytes were further characterized in detail by 1H NMR, 13C NMR, and IR spectroscopy, as well as thermogravimetric analysis. ©2005 Wiley Periodicals, Inc. J Polym SciPartA:

Polym Chem 43: 4609-4617, 2005

Keywords: functionalization of polymers; hyperbranched; polyelectrolytes

INTRODUCTION

The field of dendritic polymers, that is, den- drimers1-5 and hyperbranched polymers,6-11 has found widespread interest in the past decade. In addition to noncharged polymers, highly branched polyelectrolytes have also found strong inter- est.¹²-17 The prime example of a highly branched polyelectrolyte is polyethyleneimine. Its proper- ties in aqueous solutions strongly vary with the pH-dependent charge, which is decisive in appli- cations.¹⁸-20 The properties of charged branched topologies are also of considerable theoretical interest.^21-24Our interest in hyperbranched poly- electrolytes stems from the concept of noncova- lent binding of catalytically active metal com- plexes to soluble polymers by electrostatic inter- actions, with the aim of recovering and recycling such catalysts by means of ultrafiltration.²⁵-28

For this purpose and also other fundamental studies and potential applications, the synthesis

Correspondence to: S. Mecking (E-mail: stefan.mecking@

uni-konstanz.de)

Journal of Polymer Science: Part A: Polymer Chemistry, Va!. 43, 4609-4617 (2005)

©2005 WHey Periodicals, Inc.

of well-defined and at the same time easily acces- sible highly branched polyelectrolytes is desirable.

Particularly for catalysis, polymeric supports that are soluble in organic solvents (as opposed to water) are required most often. Hyperbranched polyglycerol can be prepared on a kilogram scale with narrow molecular weight distributions by the anionic ring-opening polymerization of glycidol.29-31 Consisting of an inert polyether scaf- fold and a large number of reactive OH groups, it is a convenient starting material for the synthesis of functionalized polymers with a hyperbranched scaffold.³2-34 In this article, we report on the syn- thesis of hyperbranched polyglycerol-based poly- cations.

RESULTS AND DISCUSSION

Synthesis and Characterization

Cationic polyelectrolytes with pyridinium and 1,2-dimethylimidazolium (1,2-DMD functional- ities were prepared by polymer analogous func- tionalization of hyperbranched polyglycerol. The 4609 Konstanzer Online-Publikations-System (KOPS)

URL: http://www.ub.uni-konstanz.de/kops/volltexte/2007/4327/

URN: http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-43275

f O H HO '>

pyridine (NMP); 80°C/48 h

1,2-dimethylimidazole NMP , 80°C/48 h [PG]-OH

= PG

o

OH HC,~

HO~

^OH3

~O'O)-O~OH

O~OyJ ^{0 0}

) ~OH)-

o _) OH

HO~ot ^{HO 0 HO}

HO OH

'"C

OH

f O H HO )

o 0

H O l O ) H O ) - A

HO ~O ^{0 - /}

OH <>-J ^HO~OH

n=2,5,7,10

Scheme 1. Synthesis of the hyperbranched pyridinium and imidazolium polycations.

Table 1. Degrees of Functionalization with Time for the Synthesis ofPG(Cs-pyr-Br)1.0^a

a Reaction conditions: 3 g of polyglycerol (40 mmol of OH), 42 mmol of 6-bromo-hexanoyl chloride in 45 mL of pyri-

din~,and a reaction temperature of 80 QC.

Determined from lHand13CNMR spectra.

ing polyelectrolyte, possessed low solubility in pyridine and precipitated during the reaction.

This hampered a complete conversion of the func- tional groups. At temperatures around 80 QC, a sufficient mixing of the viscous reaction media was ensured, but reaction times of at least 48 h were required for complete conversion, as repre- sentatively shown in Table 1 for the synthesis of PG(C5-pyr-Brh.o [general nomenclature for the designation of polyelectrolytes: PG(spacer length- cationic moiety-counterion)(degree of functionalization:

1.0=100%)].

Whereas the esterification proceeded more rap- idly, the quaternization required 2 days of reac- tion at 80 QC for complete conversion. After purifi- cation via dialysis, the polycations could be iso- lated in yields around 90%.

As expected, the degree of functionalization and thus the charge density can be controlled by the stoichiometry of the acyl chloride. For various polyelectrolytes with different degrees of func- tionalization, the experimentally observed compo- sition of the products coincides well within experi- mental error with the theoretical degrees of func- polyglycerol used in this work had a number-aver-

age molecular weight (M_{n )} of 6000 glmol (deter- mined by 13CNMR) and a polydispersity (weight- average molecular weight/number-average molec- ular weight) of 1.5 [determined by size exclusion chromatography vs poly(propylene oxide) stand- ards]. The molecular mass corresponded to an average degree of polymerization (DPn ) of 80, which is approximately equivalent to the number of hydroxy groups (when the core functionality is neglected. The number of hydroxy groups is precisely DPn

+

3, DPn corresponding to the monomer units added).

The well-known reaction of nitrogen-contain- ing heterocycles or amines with alkyl halides to form alkyl ammonium salts³⁵ was used for the synthesis of polyelectrolytes with pyridinium and 1,2-DMI functionalities. Esterification has proven to be a versatile reaction for the functionalization ofpolyglycerols.³²Reacting w-bromoacyl chlorides with polyglycerol in the presence of pyridine or 1,2-DMI allows for the functionalization of the polyglycerol scaffold and the generation of the cat- ionic moieties by quaternization simultaneously in a one-pot reaction (Scheme 1). The variation of the nature of the cationic group, the spacer length, and the control of the degree offunctional- ization allows for the synthesis of polycations with a variable charge density and flexibility.

Pyridinium Polyelectrolytes

The synthesis of pyridinium polyelectrolytes was carried out in neat pyridine as a solvent, in which polyglycerol possesses good solubility. To ensure complete functionalization, a slight excess of w- bromoacyl chloride (1.05 equiv to OH) was used.

The esterified polyglycerol, as well as the result-

Reaction Time Ch)

6 17 50

Degree of Esterification (%)b

93 97

96

Degree of Quaternization C%)b

60 83 98

Table 2. Degrees of Functionalization ^(x) of Polyelectrolytes PG(C₅-pyr-Br)x

Polyelectrolyte Theoretical PG(Cs-pyr-Brha 0.30 PG(Cs-pyr-Br)O.5 0.57 PG(Cs-pyr-Br)O.7 0.70

Esterification 27%

52%

67%

x Experimental^a Quaternization

100% (with respect to esterification) 98% (with respect to esterification) 99% (with respect to esterification)

nDetermined by 1H NMR spectroscopy.

tionalization calculated from the ratio of reagents employed (Table 2).

In the aforementioned approach, depending on the degree of functionalization, a certain portion of unreacted OH groups remains. With the poly- electrolytes employed as catalyst supports, these remaining OH groups can result in undesired side reactions. Another possibility for adjusting the charge density of the polycations is the variation of spacer length n (see Scheme 1). To this end, w- bromoacyl chlorides with alkyl spacers with 2, 7, and 10 C atoms were employed.

The syntheses of pyridinium polyelectrolytes with spacers C7 and 010 were carried out in the same way as the synthesis of PG(C₅-pyr-Br)1.0.A different protocol was required for the synthesis of PG(C₂-pyr-Br)1.o. As 3-bromopropionyl chlor- ide reacts spontaneously with pyridine, this reac- tion was carried out in two steps. Polyglycerol was first reacted with the acyl chloride in N-meth- ylpyrrolidone (NMP) at room temperature. Mter

2-3 h, a 3-4-fold (with respect to OH groups) excess of pyridine was added, and the reaction mixture was stirred for 2 days at 80-90 °C.

In all cases, complete conversions with respect to esterification as well as quaternization were observed for the syntheses ofpyridinium polyelec- trolytes with spacer lengths of 2, 5, 7, and 10 C atoms, with yields up to 90%.

Spectroscopic Characterization

The degree offunctionalization (esterification and quaternization) was determined by1H NMR spec- troscopy. A representative 1H NMR spectrum of the polyelectrolyte PG(C₅-pyr-Brh.o is shown in Figure 1.

The proton signals of the pyridinium group appear at 8.1-9.4 ppm, and those of the aliphatic spacers appear between 1.4 and 2.4 ppm. The methylene protons adjacent to the pyridinium unit give rise to a signal at 4.8 ppm.

o~

(:N+

0

^Br-

SS-O~O

^{d _}

"-O.a

~

^Br

n r b e 'N+

o gO

h i

h 9

""6 cca .c(j)

E f

~

"'C ""6

'0 c

::r:: ^co co ^.c

(,) Qi

Cl) E

I

C)_0- b c,d

e

\

^,-,

LiiII I i I1II I IIi I I II1i 11Ii I i I11i i IIiiI IIji I IIji I iIi ii iIi i Ii11I I IIIii iIi i i IIiiijIi I i iIi I I IIi i I iI

9 8 7 6 5 4 3 2 1

ppm

Figure 1. lH NMR (methanol-d_{4 ,} 300 MHz) spectrum of the polyelectrolyte PG(C5-

pyr-Brh.o.

l i t 11\ I1IIⁱI i i l l i I 'Iⁱ'·\1111'll'l!'Ii iI iIⁱI i Iji i i iIi i IiIiIi iIi IiI1

5.5 5.0 4.5 4.0 3.5 3.0

ppm

Figure 2. Comparison of the sections from 2.7-6 ppm of the IH NMR spectra of PG(Cs-pyr-Brh.o (top) and unfunctionalized polyglycerol (bottom).

prominent signal being the strong C=O absorb- ance of the ester groups at 1728 cm-1 [value for PG(C5-pyr-Brh.oJ·

1,2-DMI Polyelectrolytes

The polyelectrolytes with 1,2-DMI functionalities were prepared similarly to the aforementioned synthesis of PG(C₂-pyr-Brh.o. Polyglycerol pos- sesses low solubility in 1,2-dimethylimidazole;

thus, the reaction was performed in NMP. Poly- glycerol was first esterified with m-bromoacyl chloride; after about 2-3 h, an excess of 1,2-DMI was added at 80°C, and the mixture was stirred for 2 days. Like the pyridinium polyelectrolytes, the resulting polycation was not soluble in the reaction mixture and precipitated as a viscous solid. Polyelectrolytes with spacer lengths of 2, 5, 7, and 10 C atoms were synthesized. In all cases, the reaction resulted in full conversion with respect to esterification and quaternization, affording the final product in an 80-90% yield after purification by dialysis.

"'5 cCl!

..c:ID E

J:o

~I iCH/CH2 () (PG-scaffold)

60...

J:o

±I

()

60...

~

m

+

>-

q.

~_C\J J:()

(5

()o

~"tl

()

60...

A comparison with the 1H NMR spectrum of unfunctionalized polyglycerol (Fig. 2) shows a clear shift of the methine proton signals of the esterified secondary hydroxyl group, which can be assigned to the signal at 5.2 ppm.

The methylene protons of the esterified hydroxyl groups resonate at 4.1 and 4.3 ppm.

Because of their diastereotopic nature, they appear as two distinct signals. As expected, the other methine and methylene protons of the poly- glycerol scaffold deviate only to a small extent from the spectrum of unmodified polyglycerol, resonating as a broad signal at 3.3-3.7 ppm.

1H NMR spectra of the polyelectrolytes with C7

and C¹⁰ spacers are similar to the spectrum of PG(Cs-pyr-Brh.o shown in Figure 1, differing only in the region of the alkyl signals at 1.6- 1.1 ppm. As expected, the methylene protons of the spacer of PG(C₂-pyr-Brh.o resonate at a lower field in comparison with those of the other polyelectrolytes. The signals of the -CH2 - N+

group overlie the methine signals at 5.2 ppm. The other methylene group of the spacer resonates at 3.3 ppm. In all cases, the proton signals of unreacted hydroxyl groups were not detected in dimethyl sulfoxide (DMSO).

The Fourier transform infrared (FTIR) spectra are in accordance with expectations, the most

Spectroscopic Characterization

IH NMR spectra of polyelectrolytes with 1,2- dimethyl imidazolium bromide end groups devi- ate from the spectra of pyridinium polyelectro- lytes only by the resonance signals of the cationic group, as expected. The methylene protons of the spaceI' adjacent to the cationic group give rise to a signal at 4.2 ppm [in comparison with 4.4 ppm for PG(C₂-1,2-DMI-Brh.o]. The proton signals of the imidazolium C-C double bond occur as a broad doublet at 7.5-7.7 ppm. The methyl groups reso- nate at 3.85 (N-CH3 ) and 2.70 ppm (C-CH3 ),

respectively.

FTIR spectra of PG(Cs-1,2-DMI-Brh.o feature absorbance bands at 1587, 1539, and 1458 cm-\

which were assigned to the C=C, C=N, and C-N vibrational resonances of the 1,2-DMI group.

Synthesis of Other Polyelectrolytes

To enhance the solubility of the polyelectrolytes in organic solvents, the incorporation of aliphatic amines, namely triethylamine and tributylamine, instead of the aforementioned N-heterocycles was investigated. However, the synthesis of polycations with alkylammonium end groups by the aforemen- tioned procedure resulted only in limited conver- sions with respect to quaternization. Whereas full esterification of the OH groups of the polyglycerol

Figure 3. Structure of PG(Cs-l,2-DMI-TPPMSh.o.

scaffold was achieved, only incomplete quaterniza- tion was observed even after long reaction times of more than 5 days. A decrease in the degree of qua- ternization with increasing length of the amine alkyl chains was observed, the quaternization with triethylamine reaching a maximum of 60% conver-

. di ^{1 13}

slOn accor ng to HI C NMR measurements in comparison with 30% for tributylamine.

Whereas in studies on hydroformylation the polyelectrolytes have proven to be inert sup- ports,26 for catalysis in general and for long-term stability, the exclusion of ester groups, which can be hydrolyzed, is of interest. To this end, the reac- tion of polyglycerol with methanesulfonyl chloride resulted in a polymer with methanesulfonate end groups. The substitution of the sulfonate leaving groups by, for example, 1,2-dimethylimidazole resulted in a polyelectrolyte in which the cationic functionalities were directly attached to the poly- ether scaffold. However, ^13C NMR spectroscopic analyses revealed that only about 50% of the OH groups had been functionalized, with 85% of the terminal primary OH groups and 25% of the sec- ondary OH groups having been converted. With 4-toluenesulfonyl chloride, more than 92% of the OH groups were tosylated, but no quaternization occurred with pyridine.

Counterion Exchange

In view of their utilization as catalyst supports,p- (diphenylphosphino)benzene sulfonate (TPPMS) was introduced as a counterion into the polyelec- trolytes by exchange for the halogen counterions (Fig. 3).

The dropwise addition of an aqueous solution ofPG(C_n-1,2-DMI-Brh.o to an aqueous solution of 1.05 ionic equiv of potassium 4-(diphenylphos- phino)benzene sulfonate (KTPPMS) at 80 QC

resulted in the complete exchange of counterions, the polyelectrolyte PG(C_n-1,2-DMI-TPPMSh.o precipitating at the end of the addition. Workup by washing twice with water or alternatively purification by dialysis in methanol yielded the polyelectrolyte in yields of 70-90% (the yields varied largely because of the different water sol- ubility of the particular polyelectrolyte).

Solubility

As expected, the synthesized polyelectrolytes based on pyridinium and 1,2-DMI groups with halide counterions possess high solubility (>300 g/L) in water. They are also soluble in methanol, dimethylformamide, and DMSO and insoluble in other organic solvents such as acetone, tetra- hydrofuran, CH₂Ch, and less polar solvents. The variation of the alkyl spacer length in the range of 2-10 Catoms has little influence on their solubil- ity. The exchange of the bromide ions by TPPMS leads to polyelectrolytes that are insoluble in water but soluble in some polar organic solvents such as dichloromethane and methanol.

The solution viscosity was investigated pre- liminarily by capillary viscosimetry in salt-free aqueous solutions and 0.1 M KEr for PG(C₅-1,2- DMI-Brh.o at concentrations in the range of 10² to 5 X 10-¹ g/L. In salt-free solutions, a typical polyelectrolyte effect (well known for linear and dendritic structures^12,17,36), that is, a strong increase in the reduced viscosity with decreasing concentration, was observed.

Thermal Behavior

The thermal behavior of the hyperbranched poly- electrolytes was investigated by differential scan- ning calorimetry (DSC) with respect to the degree offunctionalization, length of the alkyl spacer, and nature of the counterions (Table 3). The highly hygroscopic nature of all the polymers required careful drying (48 h at 80 QC and 0.1 mbar) and handling under a protective gas atmosphere.

At room temperature, the polyelectrolytes are amorphous, highly viscous to glassy solids. In all cases, the polyelectrolytes show only one glass-

t~ansition temperature (T_{g ),} which is clearly hIgher than Tg of unmodified polyglycerol. No melt transitions from a conceivable side chain crystallization were observed in any case.

The flexibility of the polyglycerol scaffold decreases gradually with an increasing degree of functionalization because of the repulsive interac-

Table 3. TgValues of the Polyelectrolytes and Polyglycerol

tions of the cationic groups, and this results in an increase inTg ,as shown in Figure 4. The complete functionalization of the OH groups with alkylpyr- idinium groups [PG(C₅-pyr-Brh.oJ causes an enhancement ofTg by about 60 QC in comparison with the unmodified hyperbranched polyglycerol.

The variation of the spacer length and the nature of the counterion have an influence on Tg

as well. Using short alkyl spacers between the polyglycerol backbone and cationic groups leads to an increase in the ion density and a consider- able decrease in the chain flexibility expressed by a high T^g, as shown in Figure 5 for the imidazo- lium polyelectrolyte. An albeit less pronounced trend of a decrease in T^gwith an increasing alkyl chain length has also been observed for the pyridi- nium polyelectrolyte.

An exchange of bromide counterions inPG(C_{n -} 1,2-DMI-Br)1.o by monosulfonated triphenylphos- phine (TPPMS) lowers the influence of the spacer length on T^g. The effect of the counterions on the polymer structure andT^gdepends on the extent to which the cationic groups are shielded from one another, which is dependent on the polarizability and steric demand of the counterions. A possible explanation for the experimental findings is the formation of a closer ion pair with bromide ions in comparison with TPPMS due to their higher polar- izability. This has a greater influence at decreas- ing spacer lengths. At higher spacer lengths, the higher steric demand of the TPPMS counterions leads to a more rigid structure and a higher T^g than that observed with bromide counterions.

CONCLUSIONS

•

100 80

•

60

•

40

•

20

Degree of functionalization x[%]

Figure 4. T_gas a function of the degree of function- alization (x) for PG(C5-pyr-Br)x'

50 40 30

0'

²⁰ e...

I-^tll 10 0 -10

•

-20 0 Thermal Stability

The thermal stability of the polyelectrolytes PG(C₇-pyr-Brh.o, PG(C7-1,2-DMI-Brh.o, and PG(C₇-1,2-DMI-TPPMSh.o was investigated by thermogravimetric analysis (TGA) under a nitro- gen atmosphere (Fig. 6). No significant weight loss was observed at temperatures below 200 QC, and this confirmed the absence of low-molecular- weight impurities or water in the samples.

Whereas the unmodified polyglycerol had an onset decomposition temperature of about 350 QC (not shown in the figure), the polyelectrolytes were found to be less stable, degradation starting at 220-300 QC.

The quaternization reaction of pyridine and imidazole derivatives with alkyl halogens is reversible at higher temperatures, the facility of cleavage of the alkyl groups from quaternary salts depending on the basicity of the quaternized group and the nucleophilicity of the counter- ion.^37-39 Accordingly, the ion-exchanged polyelec- trolyte PG(C₇-1,2-DMI-TPPMSh.o (which is not capable of this reverse quaternization) has a higher thermal stability, which is close to the behavior of unfunctionalized polyglycerol with a degradation onset temperature of 300 QC.

Cationic hyperbranched polyelectrolytes can be prepared conveniently from polyglycerol in a one-pot reaction with w-bromoacyl chlorides Cl(C=O)(CH2)nBr and pyridine or 1,2-dimethyli- midazole. The density of the charged moieties, 41

49 40 29 9 31 40 80 37 40 26 54 45 46 39 -12 PG(C₂-pyr-Br)1.0

PG(C5-pyr-Brh.o PG(C7-pyr-Brh.o PG(C1o-pyr-Br)1.0 PG(C5-pyr-Br)0.3 PG(C5-pyr-Br)0.5 PG(C5-pyr-Br)O.7 PG( C2-1,2DMI-Brh.o PG( C5-1,2DMI-Brh.o PG(C7-1,2DMI-Brh.o PG(C_lO-1,2DMI-Br)1.0 PG(C₂-1,2DMI-TPPMS)1.0 PG(C5-1,2DMI-TPPMS)1.0 PG(C7-1,2DMI-TPPMS)1.0 PG(C_lO-1,2DMI-TPPMSh.o Polyglycerol (Mn = 6000g/mol)

Polymer

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

EXPERIMENTAL

Figure 5. Influence of spacer lengthn on T_g for imi- dazolium polyelectrolytes with CO) bromide and C.) TPPMS counterions.

evidenced by T_{g ,} can be varied by either the degree of functionalization or spacer length n.

The polyelectrolytes are thermally stable up to

>200 QC.

0

;g

^-20

~

Cl) -40

Cl)

0

...c+-'

-60

'050)

~ -80

-100

series thermal analysis system in the tempera- ture range of -50 to

+

100 QC at a heating and cooling rate of 10 Klmin. The reported data are second heats. Thermogravimetry was carried out on a Netzsch STA 409 instrument from 30 to 600 QC at a heating rate of 10 Klmin under a nitro- gen atmosphere. The solution viscosities were determined in aqueous solutions and 0.1 M aque- ous KBr with a Lauda PVS 1 Ubbelohde dilution viscosimeter at 20 QC with a capillary 0.53 mm in diameter.

Synthesis of the Polyelectrolytes

The general procedures for the polyelectrolyte syntheses are exemplified by the protocols employed for PG(C₂-pyr-Brh.o, PG(C₅-pyr- Brh.o, and PG(C₇-1,2-DMI-Brh.o (for complete data, cf. ref. 26).

o

^{100 200 300 400 500}

temperature[QC]

Figure 6. TGA of CD) PGCC'IPyr-Brh.o, C6JPGCC7-

1,2-DMI-Brh.o, and CO) PGCC7-1,2-DMI-TPPMS)l.o under N2 .

PG (CrPyr-Br)^1.0

To a solution of 2.54 g (34.4 mmol of OH groups) of dried polyglycerol in 20 mL of NMP, 6.07 g (35.44 mmol) of 3-bromopropionyl chloride was added dropwise under an argon atmosphere.

Mter the solution was stirred at 80 QC for 2.5 h, 25 mL of freshly distilled pyridine was added. The clear mixture was stirred for an additional 15 h at 80 QC; during this time, the product precipitated.

The obtained polyelectrolyte was purified by dial- ysis in a methanol solution, and this afforded the final purified product in a 78% overall yield.

IH NMR (300 MHz, methanol-d_4, 6): 9.24 (2H, pyr.), 8.68 (lH, pyr.), 8.20 (2H, pyr.), 5.04[CH₂-pyr o

•

9 10 o

• •

_o

2 3 4 5 6 7 8

n

o

•

80 70 60 50

Materials and General Procedures

Hyperbranched polyglycerol was supplied by Hyperpolymers GmbH.³¹ Before the functionali- zation reactions, the polymeric material was dried at 0.1 mbar at 80 QC overnight; pyridine and 1,2- dimethyleimidazole were distilled under argon.

The w-bromoalkyl acid chlorides with spacer lengths of 2,7, and 10 C atoms were prepared by the reaction of the corresponding w-bromoalkyl carboxylic acid with thionyl chloride (excess SOCl2 ,80 QC, and 3 h; yield= 75-85% after distil- lation at 0.1 mbar). KTPPMS was prepared by the method reported by Stelzer and coworkers⁴⁰,41

from 4-(fluoro)benzenesulfonic acid chloride and diphenylphosphine (overall yield

=

61%; phos- phine oxide < 3% from 31p NMR). All other reagents were purchased from Aldrich or Fluka.

For the purification of polyelectrolytes by dialysis, a benzoylated cellulose membrane with a nominal molecular weight cutoff of 1200 Da (Sigma- Aldrich) was employed.

NMR spectra were recorded in methanol-d₄ at 298 K on a Bruker ARX 300 spectrometer operat- ing at 300 eH NMR) and 75.4 MHz

e

^{3C NMR). IR}

measurements were performed on a Bruker IFS 88 FTIR spectrometer equipped with a golden- gate attenuated total reflection unit. DSC meas- urements were carried out on a PerkinElmer 7

~Ol 40 30

20- r - - - r - - , - - . . , - - - , , - - - , - - - r - - - . , . . . . - - - , - - - - , -

1

and PG-CHO(CO)], 4.5-3.2 (PG CHlCH_{2 ),} 3.33 [2H,PG-O(CO)CH_{2 -} ^]. lSC NMR (75 MHz, metha- nol-d4, ^cS): 171.5-171.0 (C=O), 147.2 (CHpyr), 146.6 (N+CH), 129.2 (CH_pyr), 79.8 (CH_pG), 75.7-66 (PG:

CHlCH2 ), 64.3 [PG-CH₂0(CO)], 58.2 (N+CH_{2 - ) ,} 36.1 [-(CO)-CH_{2 - ] .}

PG(Cs-pyr-Br)^1.0

Under an argon atmosphere, 4.49 g (60 mmol of OH groups) of dried polyglycerol was dissolved in 80 mL of freshly distilled pyridine. 6-Bromohexa- noyl chloride (1.05 equiv) was added dropwise at 80°C. Upon the addition of the acid chloride, the solution turned yellow. The reaction mixture was stirred at 80 °C for 48 h. After cooling to room temperature, the residual pyridine was decanted.

The viscous polymer was dissolved in methanol and precipitated by the pouring of the solution into a 10-fold volume of acetone. The precipitated polyelectrolyte was purified by dialysis in a meth- anol solution, and this afforded the final product in a 90% Yield.

IH NMR (300 MHz, methanol-d4,^cS): 9.18 (2H, pyr.), 8.65 (lH, pyr.), 8.19 (2H, pyr.), 5.14 [PG-CHO(CO)], 4.77 (2H, -CH2-N+), 4.5-3.2 (PGCH/CH2 ), 2.37 [2H, PG-O(CO)CH2 - ] ,2.09, 1.67, 1.47 (2H, respectively, CH₂ of alkyl spacer).

lSC NMR (75 MHz, methanol-d4, ^6): 174.6-174.2 (C=O), 146.9 (CH_pyr), 146.1 (N+CH), 129.6

(CH_pyr), 80.0 (CH_pG), 75.6-67.2 (PG: CHlCH2 ),

64.1 [PG-CH₂0(CO)], 62.7 (N+CH2), 34.8 (CO-CH2 ), 32.2/26.6/25.1 (CH2 of alkyl spacer).

ELEM. ANAL. Calcd. for C1l21HI60sN790242Br79 (26,370.88 g mol-I): C, 51.06%; H, 6.13%; N, 4.20%. Found: C, 51.89%; H, 6.36%; N, 4.32%.

PG(Cr 1,2-DMI-Br)1.o

Under an argon atmosphere, 3.0 g (40.5 mmol of OH groups) of dried polyglycerol was dissolved in 35 mL ofNMP. To the stirred solution, 1.05 equiv of 8-bromooctanoyl chloride was added, and the mixture was heated to 80°C for 2-3 h until a homogeneous solution was formed. Then, 10 mL (112 mmol) of 1,2-DMI was added, and the reac- tion mixture was stirred at 80°C for an additional 30-50 h. After cooling to room temperature, the precipitated polyelectrolyte was dissolved in methanol and reprecipitated by the pouring of the solution into a 10-fold volume of an acetone/

diethyl ether (1:1 v/v) mixture. The precipitate was further purified by dialysis, which yielded the final product in an 85% yield.

IH NMR (300 MHz, methanol-d4, ^cS): 7.6017.53 (2H, N-CH=CH-N), 5.15 [PG-CHO(CO)], 4.21 (2H, -CH₂-N+), 4.5-3.4 (PG CH/CH2),3.87 (3H, N -CHs), 2.69 (3H, C-CHs), 2.35 [2H, PG-O(CO)CH_{2 - ] ,} 1.86 (2H, CH2 of alkyl spacer), 1.62 (2H, CH2 of alkyl spacer), 1,40 (6H, CH₂ of alkyl spacer). ISC NMR (75 MHz, metha- nol-d_{4 ,} (5): 174.7-174.4 (C=O), 145.8 (C-CHs), 123.7/122.3 (N-CH=CH-N), 80.2-78.7 (CHpG),

74.5-69.4 (PG: CH/CH_{2 ),} 64.5 [PG-CH₂0(CO)J, 49.5 (N+CH2 ), 35.6 (N-CHs), 35.0 (CO-CH^{2 ),} 30.8/30.0/27.2/26.0 (CH2 of alkyl spacer), 10.0 (C-CHs)·

Funding by the Deutsche Forschungsgemeinschaft (projects Me1388/2-1 to Me1388/2-3) is gratefully acknowledged. S. Mecking is in debt to the Fonds der Chemischen lndustrie and to the Hermann Schnell Foundation for their financial support.

REFERENCES AND NOTES

1. Ca) Fischer, M.; Vogtle, F. Angew Chem lnt Ed Engl 1999, 38, 884-905; Cb) Fischer, M.; Vagtle, F.

Angew Chem 1999, 111,934-955.

2. Bosman, A. W.; Janssen, H. M.; Meijer, E. W.

Chem Rev 1999, 99, 1665-88.

3. Ca) Hecht, S.; Frechet, J. M. J. Angew Chem lnt Ed Engl 2001, 40, 74-91; (b) Hecht, S.; Frechet, J. M. J. Angew Chem 2001, 113, 76-94.

4. Ca) Oosterom, G. E.; Reek, J. N. H.; Kamer, P. C.

J.; van Leeuwen, P. W. N. M. Angew Chem lnt Ed Engl 2001, 40, 1828-49; (b) Oosterom, G. E.;

Reek, J. N. H.; Kamer, P. C. J.; van Leeuwen, P.

W. N. M. Angew Chem 2001, 113, 1878-901.

5. Van Heerbeek, R; Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Chem Rev 2002, 102, 3717-3756.

6. Flory, P. J. J Am Chem Soc 1952, 74, 2718-2723.

7. Jikei, M.; Kakimoto, M. Prog Polym Sci 2001, 26, 1233.

8. Gao, C.; Yan, D. Prog Polym Sci 2004, 29, 183.

9. Yates, C. R.; Hayes, W. Eur Polym J 2004, 40, 1257.

10. Sunder, A.; Heinemann, J.; Frey, H. Chem-Eur J 2000, 6, 2499-2506.

11. Halter, D.; Burgath, A.; Frey, H. Acta Polym 1997, 48, 30-35.

12. Turner, S. R; WaIter, F.; Voit, B. 1.; Mourey, T. H.

Macromolecules 1994, 27, 1611-1616.

13. Gong, A.; Liu, C.; Chen, Y.; Zhang, X.; Chen, C.;

Xi, F. Macromol Rapid Commun 1999, 20, 492- 496.

14. Van Duijvenbode, RC.; Rajanayagam, A.; Koper, G. J. M.; Baars,M. W. P. L.; de Waal, B. F. M.;

Meijer, E. W. Macromolecules 2000, 33, 46-52.

15. De Groot, D.; de Waal, B. F. M.; Reek, J. N. H.;

Schenning, A P. H. J.; Kamer,P. C. J.; Meijer, E. W;

van Leeuwen, :P. W N. M. J Am Chem Soc 2001, 123,8453.

16. Van de Coevering, R; Kuil, M.; Klem Gebbink, R J.

M.; van Koten, G. Chem Commun 2002,1636-1637.

17. Mori, H.; Seng, D. C.; Lechner, H.; Zhang, M.; Mul- ler, A H. E. Macromolecules 2002, 35,9270-9281.

18. Polyelectrolytes-Formation, Characterization and Application; Dautzenberg, H.; Jaeger, W.; K6tz, J.;

Philipp, B.; Seidel,C.; Stscherbma, D., Eds.; Hanser:

Munich, 1994.

19. Borkovec, M.; Koper, G. J. M. Macromolecules 1997, 30, 2151-2158.

20. Akari, S.; Schrepp, W.; Horn, D. Phys Chem Chem Phys 1996, 100, 1014-1016.

21. Welch, P.; Muthukumar, M. Macromolecules 1998, 31, 5892-5897.

22. Ramzi,A;Scherrenberg, R;Joosten, J.;Lemstra,P.;

Mortensen, K. Macromolecules 2002, 35,827-833.

23. Welch, C. F.; Hoagland, D. A Langmuir 2003, 19, 1082-1088.

24. Borisov, O. V; Daoud, M. Macromolecules 2001, 34, 8286-8293.

25. Schwab, E.; Mecking, S. Organometallics 2001, 20, 5504-5506.

26. Schwab, E. Ph.D. Thesis, Freiburg University, 2004.

27. Mecking, S.; Thomann, R Adv Mater 2000, 12, 953-956.

28. Sablong, R; Schlotterbeck, U.; Vogt, D.; Mecking, S. Adv Synth Catal 2003, 345, 333-336.

29. Sunder, A.; Miilhaupt, R (Bayer AG).WO 00/

37532, June 29, 2000.

30. Sunder, A; Hanselmann, R; Frey, H.; Miilhaupt, R. Macromolecules 1999, 32, 4240-4246.

31. www.hyperpolymers.com.

32. (a) Sunder,A; Kramer, M.; Hanselmann,R.;Mul- haupt, R; Frey, H. Angew Chem 1999, 111, 3758;

(b) Sunder,A.; Kramer, M.; Hanselmann, R.; Miil- haupt, R; Frey, H. Angew Chem Int Ed 1999, 38, 3552.

33. Sunder, A.; Bauer, T.; Miilhaupt, R; Frey, H.

Macromolecules 2000, 33, 1330.

34. Miih, E.Ph.D. Thesis, Freiburg University, 2001.

35. Menschutkin, J. J Russ Phys Chem Soc 1902, 34, 411.

36. Cohen, J.; Priel, Z. J Chem Phys 1988, 88, 7111- 7116.

37. Awad, W. H.; Gilman, J. W.; Nyden, M.; Harris, R. H., Jr.; Sutto, T. E.; Callahan, J.; Trulove, P. C.;

DeLong, H. C.;Fox, D. M. Thermochim Acta 2004, 409,3-11.

38. Challis, B. C.; Butler, A. R In The Chemistry of the Amino Group; Patai, S., Ed.; Interscience:

New York, 1968; Chapter 6, p 277.

39. Goerdeler, J. In Houben~Weyl Methoden der Organischen Chemie, 4th ed.; Muller, E., Ed.;

Thieme: Stuttgart, 1958; Vol. 11/2, Chapter 4, p 587.

40. (a) Herd, 0.; Langhans, K. P.; Stelzer, 0.; Weferl- ing, N.; Sheldrick, W. S. Angew Chem 1993, 105, 1097; (b) Herd, 0.; Langhans, K. P.; Stelzer, 0.;

Weferling, N.; Sheldrick, W. S. Angew Chem Int Ed 1993, 32, 1058.

41. Bitterer, F.; Herd, 0.; Hessler, A.; Kiihnel, M.;

Rettig, K.; Stelzer, 0.; Sheldrick, W. S.; Nagel, S.;

Rosch, N. Inorg Chem 1996, 35, 4103.